From: Kevlin Henney (kevlin_at_[hidden])
Date: 2000-11-07 12:21:39
In message <057101c048cd$f7e63a50$b9cc63a6_at_BREYED>, Ed Brey
>I think "any" should be accepted into boost.
>I have some issues for improvement of "any" that have not been addressed,
>AFAIK, in previous posts:
>1. I like exception vs. non-exception tradeoff with any_cast and copy_to.
>There are enough use cases where type mismatches are exceptional versus not,
>that it is quite worthwhile having both interfaces. I'd like to take the
>concept one step further and propose a to_ref method. It would be similar
>to to_ptr, except would return a reference and would throw upon trouble
>(much like dynamic_cast). In cases where type mismatch is exceptional,
>to_ref is more appropriate than to_ptr, since to_ref avoids giving the user
>a pointer that he's not allowed to delete.
Let me think on this one for a bit.
>2. The documentation should state that the user cannot delete the object
>pointed to by the return value of to_ptr.
Yes, good point.
>3. bad_any_cast should become any::bad_cast. One advantage would be to
>reduce the number of using declarations a user would need to be able to use
>any without boost qualifications.
It was originally like this, but on looking at the dependencies I
realised that this made the interface of any uncohesive: any::bad_cast
was unrelated to any feature in the any's interface. I moved it out, but
if we go for to_ref then it may make sense to revert.
>4. Add a templatized swap that swaps an "any" object for an
>arbitrarily-typed object, throwing on type mismatch.
Another one I'll have to think on.
>5. Negate the logic of #ifdef COMPILING_MSVC so the conforming-compiler case
>is presented first.
This was just a quick fix and I will be revisiting the macro guards
>6. Drop the using directives from the example in the documentation, and add
>"using boost::any; using boost::any_cast;". This will provide a good
>example of how code can be very readable without resorting to the
>problamatic using directive.
Kevlin Henney phone: +44 117 942 2990
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mailto:kevlin_at_[hidden] fax: +44 870 052 2289
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